Update github.com/containerd/imgcrypt to v2.0.0

Signed-off-by: Kirtana Ashok <kiashok@microsoft.com>

vendor/github.com/smallstep/pkcs7/README.md

@@ -0,0 +1,63 @@
+# pkcs7
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/smallstep/pkcs7.svg)](https://pkg.go.dev/github.com/smallstep/pkcs7)
+[![Build Status](https://github.com/smallstep/pkcs7/workflows/CI/badge.svg?query=branch%3Amain+event%3Apush)](https://github.com/smallstep/pkcs7/actions/workflows/ci.yml?query=branch%3Amain+event%3Apush)
+
+pkcs7 implements parsing and creating signed and enveloped messages.
+
+```go
+package main
+
+import (
+	"bytes"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"os"
+
+    "github.com/smallstep/pkcs7"
+)
+
+func SignAndDetach(content []byte, cert *x509.Certificate, privkey *rsa.PrivateKey) (signed []byte, err error) {
+	toBeSigned, err := NewSignedData(content)
+	if err != nil {
+		return fmt.Errorf("Cannot initialize signed data: %w", err)
+	}
+	if err = toBeSigned.AddSigner(cert, privkey, SignerInfoConfig{}); err != nil {
+		return fmt.Errorf("Cannot add signer: %w", err)
+	}
+
+	// Detach signature, omit if you want an embedded signature
+	toBeSigned.Detach()
+
+	signed, err = toBeSigned.Finish()
+	if err != nil {
+		return fmt.Errorf("Cannot finish signing data: %w", err)
+	}
+
+	// Verify the signature
+	pem.Encode(os.Stdout, &pem.Block{Type: "PKCS7", Bytes: signed})
+	p7, err := pkcs7.Parse(signed)
+	if err != nil {
+		return fmt.Errorf("Cannot parse our signed data: %w", err)
+	}
+
+	// since the signature was detached, reattach the content here
+	p7.Content = content
+
+	if bytes.Compare(content, p7.Content) != 0 {
+		return fmt.Errorf("Our content was not in the parsed data:\n\tExpected: %s\n\tActual: %s", content, p7.Content)
+	}
+	if err = p7.Verify(); err != nil {
+		return fmt.Errorf("Cannot verify our signed data: %w", err)
+	}
+
+	return signed, nil
+}
+```
+
+
+## Credits
+
+This is a fork of [mozilla-services/pkcs7](https://github.com/mozilla-services/pkcs7) which, itself, was a fork of [fullsailor/pkcs7](https://github.com/fullsailor/pkcs7).